1. Field of the Invention
The present invention relates to an ignition device for an internal combustion engine which is provided with a transformer output voltage control element that is arranged inside a high-tension tower and electrically connected to a high-voltage connection terminal and controls a voltage generated in a secondary winding in activating a transformer.
2. Description of Related Art
Conventionally, in an ignition device for an internal combustion engine disclosed, for example, in JP 2004-232466 A (FIG. 1, paragraph 0011), a noise-suppressing resistor 8 disposed in a high-tension cylinder 7 is connected at one end thereof to a high-voltage terminal 6 and at the other end thereof to a coil spring 23 which is electrically connected to an apex terminal 23. A cast insulating resin 5, which is injected into a case 4 so as to insulate and fix a transformer, is cured, whereby the noise-suppressing resistor 8 is held electrically connected to the high-voltage terminal 6 in the high-tension cylinder 7.
The noise-suppressing resistor 8 is, generally, constructed by connecting and fixing electrodes to both ends of a ceramic resistor respectively, and is used for the purpose of preventing electrical noise generated at the time of a spark discharge of the ignition plug 32 from affecting peripheral electronic components.
In the aforementioned ignition device for the internal combustion engine, however, the noise-suppressing resistor 8 and the high-voltage terminal 6 are fixed by the cast insulating resin 5 so as to prevent abrasion from being caused between the noise-suppressing resistor 8 and the high-voltage terminal 6 due to, for example, engine vibration. Thus, there have been problems in that a crack is made in the cast insulating resin 5 as a result of a difference in coefficient of linear expansion arising between the cast insulating resin 5 made of an epoxy resin and the noise-suppressing resistor 8 made of a ceramic, and the noise-suppressing resistor 8 is damaged by a thermal stress ascribable to the cast insulating resin 5.
There has also been a problem in that the noise-suppressing resistor 8 and the high-voltage terminal 6 must be electrically connected to each other through an operation in advance of injecting the cast insulating resin 5 into the case 4 with a view to preventing the noise-suppressing resistor 8 and the high-voltage terminal 6 from being brought out of electrical contact with each other due to the interposition of the cast insulating resin 5.
Further, since the cast insulating resin 5 is interposed between the noise-suppressing resistor 8 and the high-voltage terminal 6, there is also a problem in that the noise-suppressing resistor 8 is not easily replaceable alone in the market.